Impact of Preceding Crops on Incidence and Severity of Disease in Canola
Brian Jenks, North Dakota State University - $11,000

Low crop prices and severe disease problems in spring wheat have forced many producers in the Northern Plains to turn to alternative crops. Wheat production in North Dakota was down almost two million acres in 1999 compared to 1997. In contrast, canola, sunflower, dry bean, flax and pea production have been increasing in recent years. Canola acres have increased in North Dakota from 18,000 acres in 1991 to over 1 million acres in 2005.

North Dakota leads the nation in canola production. Canola has been planted in nearly every county since 1999, producing 90% of the nation’s canola.

With low prices of many crops currently grown in the Northern Plains, producers are asking whether rotations involving more profitable broadleaf crops can be shortened. Current agronomic recommendations are to plant a broadleaf crop like canola or sunflower no more than once every four years to avoid buildup of disease pathogens. However, some producers have planted a broadleaf crop like canola for two consecutive years on the same field in an attempt to increase overall profit potential. For many producers it is a matter of selecting crops that will provide them enough profit to stay in business another season. Additional information on the impact of crop rotation on disease will help producers optimize their limited resources.

Objectives:
1. Document the influence of crop rotation on the incidence and severity of sclerotinia, blackleg and alternaria black spot in canola.
2. Determine the impact of the previous crop on disease levels in canola.
3. Determine if fungicide applications can be eliminated or rates reduced by altering the sequence of crops in the rotation.